This cave in Spain — the Sima de los Huesos site — has yielded the biggest collection of ancient human fossils ever recovered from a single site.

Javier TruebaMadrid Scientific Films

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Originally published on June 20, 2014 7:54 am

Scientists have long puzzled over the origin and evolution of our closest relative, the Neanderthal. Now, researchers say Neanderthals seem to have developed their distinctive jaws and other facial features first, before they evolved to have big brains.

That's according to an analysis of 17 skulls, all taken from one excavation site in a mountain cave in Atapuerca, Spain, known as the Sima de los Huesos — the "pit of bones."

This shaft inside the cave yielded a huge number of bones, the biggest collection of ancient human fossils ever recovered from a single site. Since 1984, scientists have been painstakingly removing thousands of bone fragments and assembling them.

These skulls show Neanderthal features in the face and teeth, but have more primitive-looking braincases, according to a report in the journal Science from a research team led by Juan Luis Arsuaga of Madrid's Complutense University. The work shows that the start of the evolution of the Neanderthals began at least 430,000 years ago.

"If we understand how Neanderthals evolved and what has been going on, exactly, in the course of Neanderthal evolution, then we could say what is special with us, what is different," says Jean-Jacques Hublin, who studies human evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

While the Neanderthals were emerging, the ancestors of modern humans were evolving in Africa. Then, around 50,000 years ago, some of those modern humans ventured into Europe, where they apparently outcompeted their more-lumbering cousins, who went extinct.

Both Neanderthals and modern humans developed big brains, but they took different paths, says Hublin.

"By studying the divergence between Neanderthals and modern humans, we can understand what happened in our recent evolution," he says, "and maybe why we expanded in such a dramatic way all over the planet."

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Transcript

MELISSA BLOCK, HOST:

Now let's imagine staring into the face of a Neanderthal - think heavy brows, big jaw, they had big brains too, like our ancestors who lived alongside them for a time in Europe. But it now appears those distinctive facial features may have come before the big brains. NPR's Nell Greenfieldboyce reports on a new study of some ancient human skulls.

NELL GREENFIELDBOYCE, BYLINE: Scientists want to understand the history of Neanderthals because in some ways they were so much like us, even though they died out. The latest twist in the story of the Neanderthals comes from a mysterious place in Spain known as the Pit of Bones. Jean-Jacques Hublin has been there. He studies evolution at the Max Planck Institute for Evolutionary Anthropology in Germany. He says the Pit of Bones is deep inside a cave in the mountains.

JEAN-JACQUES HUBLIN: And it's a very impressive place to visit because you have to walk a long time underground and then to go along a rope ladder in this deep well in the dark before you get into this kind of small chapel with a bed of bones under your feet.

GREENFIELDBOYCE: The bones are from an early species of human that lived almost half a million years ago.

HUBLIN: There is only one site like this on Earth. I mean a site which is so rich in term of the number of fossils that it yields.

GREENFIELDBOYCE: He says bones from the bodies of at least 28 individuals somehow ended up at the bottom of this narrow shaft. How they got there, no one knows.

HUBLIN: It's strange. It's a mystery. It's difficult to imagine a natural scenario. My Spanish colleagues propose that actually these bodies had been thrown in this well.

GREENFIELDBOYCE: Now those Spanish researchers, along with others on their team, have painstakingly assembled and studied 17 skulls from this bone pit. In the journal Science, they say they used half a dozen different dating techniques to show conclusively that these people lived about 430,000 years ago. That makes these folks the earliest humans to have any Neanderthal-like features. They had faces that look like Neanderthals - no chins, but teeth and jaws that could open wide. Their brain cases were still small and primitive. Rolf Quam, of Binghamton University in New York, was on the research team. He says, it looks like the evolution of Neanderthals may have started with a kind of specialized chewing - why chewing? Quam says they're trying to figure that out. It must have served some purpose.

ROLF QUAM: Because it's a complex set of features, it does seem like a good candidate to represent an adaptation, rather than something that occurs randomly by genetic drift.

GREENFIELDBOYCE: Maybe they used their teeth almost like a third hand. They could hold a big hunk of meat in their jaw while they cut it, for example. There were other groups of early humans living in Europe at this time. Maybe their powerful jaws gave this particular group some kind of advantage. Quam says, all these skulls seem to be from the same species.

QUAM: We do believe that they are probably closely related. They probably are some kind of extended clan.

GREENFIELDBOYCE: Scientists are still trying to learn exactly how they're related because that might explain how they all ended up in the same pit. Nell Greenfieldboyce, NPR News.

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